<?php

/**
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; under version 2
 * of the License (non-upgradable).
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright (c) 2017 (original work) Open Assessment Technologies SA (under the project TAO-PRODUCT);
 */

use Doctrine\DBAL\Connection;

class common_persistence_sql_UpdateMultiple
{
    /** @var Connection */
    private $dbalConnection;

    /**
     * @param Connection $dbalConnection
     */
    public function __construct(Connection $dbalConnection)
    {
        $this->dbalConnection = $dbalConnection;
    }


    /**
     * @example
     *  'table_name'
     *  'data' =>
     * [
     *      [
     *          'conditions' => [
     *              'c1' => 'c1value',
     *              'c2' => 'c2value'
     *          ]
     *          'updateValues' => [
     *              'c3' => 'c3value'
     *          ]
     *      ],
     *      [
     *          'conditions' => [
     *              'c1' => 'c1value',
     *              'c2' => 'c2value',
     *              'c3' => 'c3value',
     *          ]
     *          'updateValues' => [
     *              'c9' => 'c8value'
     *          ]
     *      ]
     *  ]
     *
     * @param string $table
     * @param array $data
     * @return bool
     * @throws Exception
     */
    public function updateMultiple($table, array $data)
    {
        list($query, $params) = $this->buildQuery($table, $data);

        $stmt = $this->dbalConnection->prepare($query);
        foreach ($params as $param => $value) {
            $stmt->bindValue($param, $value);
        }

        return $stmt->execute($params);
    }

    /**
     * @param $table
     * @param array $data
     * @return array|bool
     * @throws Exception
     */
    public function buildQuery($table, array $data)
    {
        if (empty($data)) {
            return false;
        }

        $prepareQueryData = [];
        $allColumns       = [];
        $params           = [];

        foreach ($data as $row) {
            $this->assertValidRow($row);
            $conditions = $this->extractConditions($row);
            $updateValues = $this->extractValuesToUpdate($row);

            foreach ($updateValues as $updateColumn => $updateValue) {
                $prepareQueryData[$updateColumn][] = [
                    'value' => $updateValue,
                    'conditions' => $this->extractWhensConditions($conditions)
                ];
            }
        }

        $queryColumns = [];
        foreach ($prepareQueryData as $column => $queryData) {
            $queryColumnUpdate = " $column = ( CASE ";

            foreach ($queryData as $index => $datum) {
                $conditions = $datum['conditions'];
                $updateValue = $datum['value'];
                $conditionsString = [];

                foreach ($conditions as $indexCondition => $condition) {
                    $conditionColumn = $condition['conditionColumn'];
                    $conditionValue = $condition['conditionValue'];

                    $key = ':' . $index . '_' . $column . '_'  . $indexCondition . '_' . $conditionColumn . '_conditionvalue';
                    $conditionsString[] = " $conditionColumn = $key ";
                    $allColumns[$conditionColumn][] = $conditionValue;
                    $params[$key] = $conditionValue;
                }

                $key = ':' . $index . '_' . $column . '_updatedvalue';
                $queryColumnUpdate .= " WHEN " . implode(' AND ', $conditionsString) . " THEN $key";
                $params[$key] = $updateValue;
            }

            $queryColumnUpdate .= " ELSE $column END)";
            $queryColumns[] = $queryColumnUpdate;
        }

        $query = 'UPDATE ' . $table . ' SET ' . implode(', ', $queryColumns);
        $wheres = [];

        foreach ($allColumns as $columnWhere => $columnWhereValues) {
            $uniqueColumnValues = array_unique($columnWhereValues);
            $placeHolders = [];
            foreach ($uniqueColumnValues as $index => $value) {
                $key = ':in_condition_' . $columnWhere . '_' . $index;
                $placeHolders[] = $key;
                $params[$key] = $value;
            }
            $placeHolders = implode(',', $placeHolders);
            $wheres[] = " $columnWhere IN ($placeHolders)";
        }

        $query .= ' WHERE ' . implode(' OR ', $wheres);

        return [$query, $params];
    }

    /**
     * @param $row
     * @throws Exception
     */
    private function assertValidRow(array $row)
    {
        if (empty($row['conditions']) || empty($row['updateValues'])) {
            throw new Exception('You must provide conditions and updateValues');
        }
    }

    /**
     * @param $conditions
     * @return array
     */
    private function extractWhensConditions($conditions)
    {
        $whens = [];
        foreach ($conditions as $conditionColumn => $conditionValue) {
            $whens[] = ['conditionColumn' => $conditionColumn, 'conditionValue' => $conditionValue];
        }

        return $whens;
    }

    private function extractValuesToUpdate($row)
    {
        return $row['updateValues'];
    }

    private function extractConditions($row)
    {
        return $row['conditions'];
    }
}